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IP over DWDM

IP over DWDM. NANOG May 24, 1999. Larry McAdams lmcadams@cisco.com. Outline. Optical Transmission Fundamentals DWDM Systems IP over DWDM. Its Analog Transmission. Attenuation. Dispersion. Nonlinearity. Reflectance. Transmitted data waveform. Waveform after 1000 km.

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IP over DWDM

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  1. IP over DWDM NANOG May 24, 1999 Larry McAdams lmcadams@cisco.com

  2. Outline • Optical Transmission Fundamentals • DWDM Systems • IP over DWDM

  3. Its Analog Transmission Attenuation Dispersion Nonlinearity Reflectance Transmitted data waveform Waveform after 1000 km

  4. Fiber Attenuation • Telecommunications industry uses two windows: 1310 & 1550 • 1550 window is preferred for long-haul applications • Less attenuation • Wider window • Optical amplifiers 1550 window 1310 window l

  5. Fiber Dispersion Normal fiber Non-dispersion shifted fiber (NDSF) >95% of deployed plant 18 Wavelength l 0 Dispersion ps/nm-km 1310 nm 1550nm Reduced dispersion fibers Dispersion shifted fiber (DSF) Non-zero dispersion shifted fibers (NZDSF)

  6. Interference Dispersion • Dispersion causes the pulse to spread as it travels along the fiber • Chromatic dispersion is important for singlemode fiber • Depends on fiber type and laser used • Degradation scales as (data-rate)2 • Modal dispersion limits use of multimode fiber to short distances

  7. Polarization Mode Dispersion • Most severe in older fiber • Caused by several sources • Core shape • External stress • Material properties • Becomes an issue at OC-192

  8. Four-Wave Mixing (FWM) • Creates in-band crosstalk that can not be filtered • Problem increases geometrically with • Number of ls • Spacing between ls • Optical power level • Chromatic dispersion minimizes FWM

  9. Outline • Optical Transmission Fundamentals • DWDM Systems • IP over DWDM

  10. 40-80 km Terminal Terminal Regenerator - 3R (Reamplify, Reshape and Retime) 120 km Terminal Terminal EDFA - 1R (Reamplify) Terminal Terminal Terminal Terminal Terminal Terminal EDFAs Enable DWDM EDFA amplifies all ls

  11. ... ... EDFA Schematic • EDFAs amplify all ls in 1550 window simultaneously • Key performance parameters include • Saturation output power, noise figure, gain flatness/passband EDF EDF WDM Coupler WDM Coupler Optical Filter Optical Isolator Optical Isolator DCF 1480 Pump Laser 980 Pump Laser

  12. 15xx nm 1310 nm 1310 nm Reamplify Reshape Retime Rx Tx External Modulator Laser Rx DWDM System Design 1550 0 0 1551 1 1 1552 2 2 1553 3 Optical Combiner 3 DWDM Filter 1554 4 4 1555 5 5 Amplify 1556 6 6 1557 7 7 15xx nm

  13. DWDM State-of-the-Art • Point-to-point systems • 40l x OC-48 deployed • 16l x OC-192 deployed • 160l x OC-192 announced • Configurable OADMs • Metro rings Data Rate 1-10 Tbps per fiber is just around the corner!

  14. Outline • Optical Transmission Fundamentals • DWDM Systems • IP over DWDM

  15. Synchronization for IP over DWDM ~ ~ ~ ~ ~ ~ FIBER • Point-to-point application • Synchronization driven from router • Router interface internal timed WDM REGEN OC-48c OC-48c DS1 Ethernet Ethernet Gig-Ethernet OC-3c T1 OC-12c SONETNETWORK OC-48c OC-48c PRS • SONET network application • Synchronization driven from network • Router interface timed to PRS via Rx OC-48c

  16. Protection for IP over DWDM • Optical protection is not sufficient • Only protects transmission infrastructure • Layer 3 must provide path restoration • Opportunity for differentiation at the service level Optical Cloud

  17. 100 km 25 dB 500 km Ciena 40l DWDM GSR 12000 SR OC-48 PoS RC TX RC TX RC TX RC TX GSR 12000 SR OC-48 PoS TX RC Error-free transmission over 20,000 kms without SONET regeneration

  18. Working Protect PRS Nortel 16l DWDM and OC-192 Ring Lack of transponders prohibits direct connections at OC-192

  19. Conclusion - IP over DWDM • Transmission is an analog problem • Proprietary solutions abound • DWDM provides 100s Gbps of capacity • Transponders are required for an open architecture • Large scale deployments have been achieved • IP directly over DWDM is a reality

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